P0301 Misfire Detected in #1 Cylinder

Please forgive me as I can not type Chinese on the PC I am using.

Background:  About a year ago I replaced the 4 spark plugs for my 2012 Subaru Legacy. It took me a while to unscrew the old spark plugs and took them out but when I tightened the new spark plugs pretty soon I felt it was already tight and I did not go any further because I did not want to overtighten them.  Several days alter my check engine light was on and the code was P0301 Misfire Dected in #1 Cylinder. I tried to tighten the spark plug again but it was still pretty tight so I just erased the code and the car was running fine for about a year. 

recently the code P0301 came back again and if I erased it the check engine light will turn on again the next day. Now what can I do? I can bring the car to a dealership but just feel it is stupid if the problem is the spark plug is not tighten enough. Should I just try unscrewing the spark plug and tightening it again and see how it goes?  Or should i just let a mechanic to handle it?

 

Thanks!